four alphabets alphabetical order in c

The program must accept four alphabets as the input. If the four alphabets are in alphabetical order print YES as the output. Else print NO as the output.

Example Input/Output 1:
Input:
a c e r

Output:
YES

solution:

int main()

{

char a,b,c,d;

scanf("%c %c %c %c",&a,&b,&c,&d);

if(a<b&&b<c&&c<d){

    printf("yes");

}

else{

    printf("no");

}

}